In approximately three weeks from now, India should enter a new realm of achievement in space. The Indian Space Research Organisation's first Geo Synchronous Launch Vehicle is expected to take its first developmental flight in the last days of March. It will be launched from the ISRO launch pad at Sriharikota, 80 kilometres north east of Madras, on the Andhra coast. Even as you read this, integration, preparation and the checking of the launch vehicle is proceeding at a frenetic pace at Sriharikota.

What makes the GSLV so special and so different from all the other launchers that ISRO has developed and used so far? Simply put, its size and scale. This launcher, which can put heavy communication satellites into orbit, is the first one to be indigenously developed in India. It is the final step in an arduous, five decade long journey that began as the dream project of then ISRO chairman, Dr Vikram Sarabhai. Unfortunately, it took a decade more than what he had estimated before the GSLV was actually ready. But, given the setbacks that plagued the programme, the delay was understandable.

The GSLV is the launch vehicle that will finally give the Indian space programme true independence and self reliance. No longer will we have to depend on France's Arianespace or American launchers to send up communication satellites like the INSAT (INSAT stands for Indian National Satellite.) India will finally be able to make her own satellites, launch them into orbit and sustain them during their lifespan.

For a country such as ours, this is certainly no mean achievement, especially when one takes the commercial implications into consideration. ISRO will soon have the capability to become another Ariansespace and hire out its facilities. Until now, all we have been able to do is sell data from some of our remote sensing satellites to other countries.

Now, finally, the GSLV is ready for use. ISRO has revealed all its specifications, structure, fuel systems and mission statement, which rediff.com brings to its readers.

The GSLV is a three-stage vehicle, 49 metres tall. Its first stage consists of a solid propellant motor and four liquid propellant strap-on stages. Its second stage is fuelled by a single liquid propellant engine. The third stage, which is what really differentiates it from the earlier generations of launchers, is a cryogenic stage with restartable engines.

It was at this stage that Russia, over a decade ago, let India down badly. They had initially promised India the knowhow to build these cryogenic engines. Later, under pressure from the US, they backed down, finally agreeing only to supply some ready engines and not the technology that would enable India to build them indigenously. Incidentally, the cryogenic engine being used in this GSLV flight is imported, but ISRO is now able to build these engines as well.

The GSLV is basically designed to place satellites in a Geo Synchronous Transfer Orbit. It uses the solid and liquid stages of ISRO's Polar Satellite Launch Vehicle, which have repeatedly proven their worth in successful flights (The PSLV, the precursor to the GSLV, did not have the cryogenic engines.)

The first stage is 2.8 metres in diameter and is made of M250 grade maraging steel. It has a nominal propellant loading of 129 tonnes. Each L40 is loaded with 40 tonnes of hypergolic propellants (UDMH & N2O4) stored in two independent tanks which are 2.1 metres in diameter and has a pump-fed engine that provides 680 kN thrust.

The second stage is 2.8 metres in diameter and is loaded with 37.5 tonnes of liquid propellants (UDMH & N2O4 ) in two compartments of aluminium alloy stage tankage, separated by a common bulkhead. This has a pump-fed engine that provides 720 kN thrust.

The third stage is 2.8 metres in diameter and uses liquid hydrogen (LH2) and liquid oxygen (LOX) in two separate tanks of aluminium alloy interconnected by an inter-stage structure. The total propellant loaded in this stage is 12.5 tonnes.

The overall length of the launch vehicle is 49 metres. Its lift-off weight will be 401 tonnes. Its Geo Synchronous Transfer Orbit will be 180 x 36,000 kilometres.

Developmental flights of launchers seldom carry valuable payloads or satellites. This flight will be no exception. It will not carry an INSAT, even though it has the capacity to launch one. Instead, it will take up an experimental communication satellite, the 1,530 kilogramme GSAT1, which will be used for demonstrating digital audio broadcast, Internet services, compressed digital television experiments and developmental communication. It will also attempt to test new spacecraft elements like 10 Newton reaction control thrusters, fast recovery star sensors and heat pipe radiator panels.

This satellite will also carry two C-band transponders with 10W Solid State Power Amplifiers for India coverage, two C-band transponders with a 50W transponder using Travelling Wave Tube Amplifiers for India and South Africa coverage and two C/S-band transponders using 70W TWTA.

The GSLV has an aluminium alloy heat shield. It consists of two halves, has a diameter of 3.4 metres and is 7.8 metres long. This heat shield is designed to protect the spacecraft from hostile flight environments during each ascending phase.

If all goes well on March 28 or 29, and the first developmental flight -- virtually a test flight -- is successful, ISRO will launch its next GSLV in possibly a year's time. After that, they will be able to do at least one GSLV launch a year from Sriharikota, which should give the Indian space programme total autonomy and self-reliance. Commercialising the launch facilities will then be a very possible option, even though it may be a low priority; after all, India herself may well want to launch a communication satellite a year.